Catheter introducer system for exploration of body cavities

ABSTRACT

A self propelling catheter introducer system for exploring a body cavity is disclosed which includes a flexible tubular catheter, a propulsion section and a steering section located near the end of the catheter that is introduced in a body cavity. The propulsion section includes a flexible everting tube designed to push the catheter from inside the body cavity. The catheter can thus be made very flexible in bending, and a larger diameter catheter can be used without discomfort to the patient.

RELATED APPLICATIONS

[0001] This is a continuation in part of U.S. patent application Ser.No. 09/492,448, filed on Jan. 27, 2000.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a method and a device forperforming endoscopy through a catheter introducer system. Inparticular, the present invention relates to a catheter introducersystem for endoscopy designed to reach the cecum portion of thegastrointestinal tract.

DESCRIPTION OF RELATED ART

[0003] Endoscopy has become an increasingly important tool in diagnosingand in treating ailments of the gastrointestinal tract, also referred toas the GI tract. Typical endoscopes are essentially formed by a somewhatflexible tube that is pushed through the GI tract, after beingintroduced in the body cavity starting from the rectum or starting fromthe esophagus. The endoscope has a steerable tip to facilitatenavigation through the GI tract, and typically has to be sufficientlystiff so that it can be pushed further along the body cavity. The tip ofthe endoscope that is introduced in the GI tract can be outfitted withseveral devices, most notably an illumination device and a visiondevice, such as a vision integrated circuit, so that the operator of theendoscope can observe the interior of the GI tract and maneuver theendoscope in the proper position.

[0004] Once the endoscope is in position, other tools attached to theendoscope or inserted through the endoscope can be brought to the properposition in the GI tract. Various procedures can then be carried out,such as removing polyps, performing sutures, irrigation, suction, andremoving other tissues. The various tools that are used together withthe endoscope can be either inserted separately in the GI tract andplaced in the proper position independently, or may travel in a workingchannel of the endoscope, so that once the endoscope is positioned atthe desired location in the GI tract, the tools inserted in theendoscope will also easily reach that position.

[0005] Endoscopes or other smaller similar devices can also be used toexplore other body cavities, for example airways or blood vessels. Theseprobes must be small to fit in the smaller cavities, and care must betaken to avoid damage to the more fragile membranes lining thesecavities.

[0006] Current state of the art endoscopes are very capable devices, andendoscopy has been very successful in diagnostic and therapeuticapplications with the use of current endoscopes and the current arsenalof tools that can be inserted through the working channel of theendoscope, or can be attached to the outside of the endoscope. However,current endoscope technology has limitations and drawbacks. One of thegreatest drawbacks of current endoscopes is that the working channel issmall. The working channel is small relative to overall diameter of theendoscope, and is further limited by the space taken up by vision,irrigation, suction, light, and control cabling mechanisms that are partof the endoscope and are required to control the endoscope. Thus thereis a very small area left for other tools to be introduced through theendoscope.

[0007] Current endoscopes are also difficult to maneuver, particularlywhen the endoscope has to be pushed from outside the body all the way toa far portion of the intestine, such as the cecum, located at thebeginning portion of the large intestine. Currently, reaching the cecumrequires training, skill, luck and trial and error on the part of theoperator. Current endoscopes have to be maneuvered by pushing them fromoutside the body into the gastrointestinal tract, while steering the farend inside the body cavity. This situation creates an inherentlyunstable condition, where a long tube is being pushed through a narrowcavity. This requires the endoscope tube to be rather rigid, resultingin discomfort to the patient as the endoscope is maneuvered. Because ofthis, the patient often must be sedated.

[0008] Once the cecum has been reached, additional tools still have tobe navigated through the body to reach the location, and if theendoscope is withdrawn from that location to make room for other tools,access has to be reestablished using the same complicated procedure.Current endoscopes tend to be reusable because of the high cost of theircomponents, and thus require thorough cleaning to sterilize them.Sterilization can be difficult to guarantee, and in many instances adisposable device would be preferable.

[0009] Accordingly, there is a need for an improved type of endoscopewith a introducer system that obviates some of the drawbacks ofcurrently known endoscopes.

SUMMARY OF THE INVENTION

[0010] The present invention is directed to a catheter introducer systemfor endoscopy that substantially obviates one or more of the problemsdue to limitations and disadvantages of the related art, and that can beused more easily and with less discomfort to the patient. Additionalfeatures and advantages of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Otheradvantages of the invention will be realized and obtained by theapparatus and method particularly pointed out in the written descriptionand claims hereof, as well as the appended drawings.

[0011] To achieve these and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described, theinvention discloses a self propelling catheter introducer system forexploring a body cavity that includes a flexible tubular catheter havinga length extending from a distal end for introduction in the cavity to aproximal end opposite the distal end, a tubular working channel formedwithin the catheter, adapted for guiding medical tools along the lengthof the catheter, and a steering section of the catheter disposedadjacent the distal end, adapted for pointing the distal end in adesired direction. In addition, the system includes a flexible evertingtube disposed at the distal end that applies a propulsive force to thetubular catheter, and control unit for controlling operation of theeverting tube and of the steering section. Examples of everting tubeapparatus are illustrated in U.S. Pat. Nos. 5,259,364 and 5,586,968,both to Bob et al.

[0012] In another aspect, the invention discloses a method of propellinga catheter for exploring a body cavity, the catheter having an outersurface including a flexible everting tube. The method comprisesinserting a distal end of the catheter through an opening of the bodycavity, securing an anchor portion of the catheter to the opening, thecatheter being slidable in the anchor portion and a surface of theeverting tube being secured to the anchor portion, and translating theeverting tube relative to the anchor portion, thus inserting orwithdrawing the catheter in the body cavity.

[0013] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitutepart of the specification, illustrate several embodiments of theinvention and together with the description serve to explain the presentinvention. In the drawings:

[0015]FIG. 1 illustrates a first embodiment of the catheter introducersystem for endoscopy according to the invention;

[0016]FIG. 2 illustrates a detail of the distal end of the cathetershown in FIG. 1;

[0017]FIG. 3 illustrates a portion of a second embodiment of thecatheter introducer system according to the invention;

[0018]FIG. 4 illustrates a portion of another embodiment of the catheterintroducer system according to the invention;

[0019]FIG. 5 is a side elevation showing one embodiment of asteering/propulsion section according to the invention;

[0020]FIG. 6 is a perspective view showing a detail of one embodiment ofa gripper portion;

[0021]FIG. 7 is a front and side view of a first embodiment of a suctionring according to the invention;

[0022]FIG. 8 is a front, perspective and side view of a secondembodiment of a suction ring according to the invention;

[0023]FIG. 9 is a front, perspective and side view of a third embodimentof a suction ring according to the invention;

[0024]FIG. 10 is a front and side view of a fourth embodiment of asuction ring according to the invention;

[0025]FIG. 11 is a front and side view of a fifth embodiment of asuction ring according to the invention;

[0026]FIG. 12 is a front, perspective and side view of a sixthembodiment of a suction ring according to the invention;

[0027]FIG. 13 is a front and side view of a seventh embodiment of asuction ring according to the invention;

[0028]FIG. 14 is a front, perspective and side view of an eightembodiment of a suction ring according to the invention;

[0029]FIG. 15 is a front, perspective and side view of a ninthembodiment of a suction ring according to the invention;

[0030]FIG. 15b is a top view of a variation of the embodiment shown inFIG. 15.

[0031]FIG. 16 is a diagram showing the interaction of body tissue with asuction hole according to one embodiment of the invention;

[0032]FIG. 16b is a diagram showing the interaction of body tissue witha suction hole according to another embodiment of the invention;

[0033]FIG. 17 is a top and perspective view of a tenth embodiment of asuction ring according to the invention;

[0034]FIG. 18 is a top view of an eleventh embodiment of a suction ringaccording to the invention;

[0035]FIG. 19 is a schematic side view showing the steering/propulsionsection according to one embodiment of the invention;

[0036]FIG. 20 is a perspective view of a twelfth embodiment of a suctionring according to the invention;

[0037]FIG. 21 is a perspective view of a thirteenth embodiment of asuction ring according to the invention;

[0038]FIG. 22 is a schematic sectional side view showing a differentembodiment of the propulsion section according to the invention; and

[0039]FIG. 23 is a schematic sectional side view showing a furtherembodiment of the propulsion section.

DETAILED DESCRIPTION OF THE INVENTION

[0040] The catheter introducer system according to the present inventionconsists of a large catheter having an outer diameter that may becustomized to fit within the portion of body cavity into which it is tooperate, for example the colon, esophagus, or other part of the GItract. The catheter may be customized to the size of body cavities ofindividual patients. A steerable tip is included at the distal end ofthe catheter that is introduced in the body cavity, so that the devicecan easily travel inside the GI tract or other body cavity that is thesubject of the procedure. A propulsion section may also be included nearthe distal end of the catheter, that operates by pulling the distal endthrough the body cavity, so that the rest of the device is also pulledalong, or by pushing the distal end from inside the body cavity. In thismanner, a very flexible catheter tube can be used. A more flexiblecatheter results in less discomfort to the patient, and can thus be madeof a larger diameter than a rigid catheter could be made. The patientalso does not have to be sedated for this procedure.

[0041] The catheter introducer system has several functions, includingnavigation and maneuvering in the GI tract, providing light and visiondevices to see the areas surrounding the tip of the catheter, providingsuction, irrigation and tissue extraction, transporting devices forimage acquisition such as optical and ultrasound sensors, and providinga working channel and tool manipulation for various endoscopy tools.

[0042] Because of the design of the catheter according to the presentinvention, a larger diameter tube can be used, so that a large workingchannel is provided for introduction and maneuvering of other tools usedduring endoscopic procedures. The propulsion and steering sections allowthe catheter to maneuver easily in the colon, or in other parts of theGI tract, including hard to reach parts such as the cecum. Once thecatheter is positioned near the area of the GI tract of interest, it canremain there while various tools are introduced through the workingchannel, and thus access to the affected area of the GI tract can easilybe accomplished by successive and different tools. Many components ofthis catheter introducer system are disposable, thus obviating some ofthe problems due to difficult sterilization procedures.

[0043]FIG. 1 illustrates a first embodiment of the endoscopy deliverycatheter according to the invention. Catheter introducer system 1includes a flexible tubular catheter 2 having a distal end 4 and aproximal end 6. Distal end 4 is the end of the catheter that isintroduced in the body cavity, while proximal end 6 is at the oppositeend from distal end 4 and remains outside of the body cavity. Flexiblecatheter 2 is hollow on the inside, thus defining a working channel 10that extends from proximal end 6 to distal end 4. Since the catheter 2is very flexible, it can have a large diameter, so that a large workingchannel 10 is provided for introduction and maneuvering of endoscopytools 8.

[0044] In a preferred embodiment, the working channel is defined by asheath 11, which is non-collapsible and thus tends to maintain acircular cross section even when it is bent along its axis. Sheath 11can also include a coil to help maintain its cross sectional shape. Theworking channel tends to retain a constant size when sheath 11 is used,so that binding of the tools inserted in the working channel 10 isprevented, and the outer surface of catheter 2 can be very light andflexible. For example, the working channel can have a diameter of about14 mm, resulting in an outer diameter of the device of about 20 mm.

[0045] Various types of tools 8 can be inserted through the workingchannel 10, so that once catheter 2 is in position within the bodycavity, additional endoscopy tools can quickly and easily reach the areaof interest within the GI tract. Any present tool for endoscopy can beadapted for use in the working channel 10 of catheter 2, and the largecross section of working channel 10 opens the possibility of developingnew tools and procedures that can improve the function of currentdevices. In a preferred embodiment, the catheter portion 2 can bedisposable, so that cleanliness and sterilization of the catheterintroducer system can be assured.

[0046] In addition to tools 8 that can be introduced through thecatheter introducer system 1, some other devices can be built-in withincatheter 2. For example, a vision chip 12 such as a charge coupleddevice (CCD) or a CMOS and light source 14 can be built in the catheter,as well as an accessory 16 that may perform suction, irrigation, orother functions. In addition to a vision chip 12, other sensors could beprovided on the catheter introducer system 1. For example, X-ray orultrasound sensors could be utilized.

[0047] In a preferred embodiment, vision chip 12 and light source 14 canbe part of a modular vision tool 13 that can be detached from catheter 2and replaced. For simplicity, vision tool 13 could snap in place at thefront of catheter 2, so that electrical or other connections would bemade automatically. Using a snap-on vision tool 13 facilitatessterilization of the device, because most components of the catheterintroducer system 1 other than vision tool 13 could be made disposable.If a CCD is used in vision tool 13, only thin wires need to connect theCCD to the proximate end of the catheter 2. Catheter 2 thus remainsflexible and can be manufactured cheaply. If necessary, a fluid supplycould be provided to the CCD lens, to clean it of contaminants.

[0048] The catheter portion can be provided with a rectal sheath 20 madeof a more rigid material and located at the entrance of the body cavity,for example to prevent the sphincter from compressing and binding theflexible catheter. Sheath 20 is designed to maintain the sphincter in anopen position and allow the catheter to move back and forth freely. Thesheath may also provide a seal with the outer surface of the catheter.This seal is particularly useful when air is used to inflate the colon,to facilitate the visual inspection. In a further embodiment accordingto the invention, an active sheath can be used to assist the motion ofthe catheter, by pushing and pulling on the catheter, for example withan endless screw mechanism, rack and pinion mechanism, or axial andradial actuators of known type.

[0049] The catheter introducer system shown in FIG. 1 includes apropulsion section 22 that is located near the distal end 4 of catheter2. The propulsion section 22 is designed to pull the portion of catheter2 near it through a body cavity, so that the catheter 2 can easilynavigate through a cavity like the GI tract. Since propulsion section 22is designed to pull from within the body cavity, catheter 2 can be moreflexible than would be possible if the catheter were pushed from outsideof the body cavity, because catheter 2 does not have to transmit thecompression loads caused by being pushed. As a result, this devicereduces the pain and discomfort felt by the patient, because the devicecan be made extremely flexible in bending while also having a largediameter. Propulsion system 22 includes several sliding gripping pads 24that can travel along guides 26 in an axial direction, along the lengthof the catheter 2. Gripping pads 24 are located on an outer surface ofcatheter 2, and in one embodiment are distributed evenly around thecircumference of the catheter 2. In the preferred embodiment shown inFIG. 1, gripping pads 24 have suction ports 25 so that they can attachto the inside surface of the body cavity whenever a vacuum is applied tothe suction port 25.

[0050] In a preferred embodiment according to the invention, each one ofgripping pads 24 can move along guide 26 independently, and the suctionapplied to each of suction ports 25 can be turned on or offindependently from that of the other suction ports 25. In a morepreferred embodiment, four gripping pads 24 are provided in four slidingchannels 26, one in each channel, and are spaced about 90° apart fromeach other around the circumference of catheter 2. Opposing pairs ofgripping pads 24 can be coordinated to move and apply suction in unison.

[0051] During operation of the propulsion section 22, the gripping pads24 move in coordinated manner, gripping, releasing, and sliding to movethe catheter 2 forward and backward. To move forward, for example,approximately half of the pads 24 in a first group located at the firstposition A in sliding channel 26 apply a vacuum through suction ports25, so that they become attached to the tissue of the body cavity. Atthe same time, a second group of gripping pads 24 is moved to a secondposition B in sliding channel 26, without vacuum being applied to theirsuctions ports 25. In this phase air may be expelled through the movingsuction ports, to ensure that body tissue does not stick to the movinggripping pads 24. This makes it easier for the gripping pads 24 to slidealong the cavity wall. A saline solution or other fluid may also beexpelled through suction ports 25, to remove any contaminants from theports.

[0052] Once the second group of gripping pads 24 reaches position B, thevacuum is turned on to the ports 25 of those gripping pads, which attachto the tissue of the body cavity. Vacuum is at the same time turned offto the first group of gripping pads 24 at position A. At that pointgripping pads 24 at position B are moved to position A, whilemaintaining the suction, so that the entire catheter 2 is pulled forwardrelative to the body cavity tissue by a distance substantially equal tothe distance between points A and B of sliding channel 26.

[0053] To move backwards, for example, the same sequence can be carriedout in reverse order, so that the group of gripping pads 24 to which avacuum is applied are initially moved from point A to point B of thesliding channel 26, to force the catheter 2 out of the body cavity.

[0054] Vacuum can be applied to suction ports 25 by turning on and off aconnection to a vacuum source 31. The sliding movement of gripping pads24 and suction ports 25 within sliding channel 26 can be performed in avariety of manners, such as by mechanical movement of push-pull wires30, with force from an inflating bellows, or by activation of linearactuators that respond to electricity or other changes in theiroperating environment. Movement of gripping pads 24 within slidingchannel 26 can also be accomplished in other known manners, such as byusing shape memory actuators, piezoelectric actuators, or other types ofactuators commonly known as artificial muscles.

[0055] The application of a vacuum to the various suction ports 25,movement of gripping pads 24 within sliding channels 26, and othercontrol functions can be performed by hand or, in a preferredembodiment, by a control unit 34 that automatically coordinates themovement of the individual suctions pads in the sliding channels andapplication of suction in response to instructions of the operator ofthe catheter system. The operator, for example, could select movement ofthe catheter in or out of the cavity, and control unit 34 could operatepropulsion section 22 accordingly. Control unit 34 could include, forexample, a memory containing sequences of instructions for movement andapplication of vacuum by the gripping pads 24, that result in desiredmovement of the catheter 2. Control unit 34 could also include anelectronic computer to convert those sequences into commands for servomotors, valves, and other actuators that affect the operation ofgripping pads 24, and control supply of vacuum from vacuum source 31 viaducts 33.

[0056] Each of gripping pads 24 could also have more than one suctionport 25 applying vacuum to the body cavity tissue. A perforated surfacecould be used instead of an individual port, having a configuration thatwill be described in detail below, in the context of a perforatedsuction ring.

[0057] In yet another embodiment, different methods for gripping theinside of the body cavity could be used instead of the suction pads 24.For example, inflatable balloons could grip the tissue of the bodycavity when inflated, and could be operated in the same manner as thegripping pads with suction ports.

[0058] The catheter introducer system shown in FIG. 1 includes asteering section 36 also located adjacent to the distal end 4 of thecatheter 2. In the preferred embodiment the steering section 36 iscloser to the opening of the distal end 4 of the catheter than thepropulsion section 22. However, the opposite arrangement can also beutilized successfully. Steering section 36 allows an operator to changethe direction where distal end 4 is pointed inside the body cavity. Inthe preferred embodiment shown in FIG. 2, the steering section 36comprises a flexible structure, such as a braid or mesh 37, that definesthe outer circumferential surface of the tube-like catheter 2. Flexiblemesh 37 can be collapsed and can also be extended to several times itscollapsed length in a direction along the length of the catheter 2. In apreferred embodiment, steering section 36 is formed of a flexible meshtube having similar properties to those of an endoscopic or vascularstent, such as, for example, the Wallstent manufactured by BostonScientific Corporation. The flexible mesh tube is designed to providesufficient rigidity to maintain a tube-like shape, while also allowing achange in length of the section.

[0059] The tube formed by flexible mesh 37 can also be bent in a desireddirection by stretching mesh 37 in one circumferential portion whilecompressing it on the opposite circumferential portion of the tube.Steering section 36 can thus be turned in a selected direction withrespect to the center line of the catheter 2.

[0060] The stretching and turning of flexible mesh 37 can be carried outin a convenient manner by using push-pull cables 38, shown in FIG. 2.Push-pull cables 38 are sufficiently stiff such that they can carry atension as well as a compression load, and are attached to tip 40forming the distal end 4 of catheter 2. Tip 40 can preferably be made ofaluminum or plastic. In a preferred example, push-pull wires 38 are madeof NITINOL, which is a super-elastic alloy that resists elasticdeformation leading to the formation of kinks. For disposable catheters,the wires 38 can alternatively be made of steel, or other materials thattend to regain their original shape after bending. However, NITINOLwires are preferred for applications where catheter 2 is usedrepeatedly.

[0061] Aluminum tip 40, flexible mesh 37, and push-pull wires 38 are alldisposed on the circumference of catheter 2, so that working channel 10is left free for introduction of endoscopy tools. Push-pull cables 38exit the body cavity and exit from catheter 2 at the proximal end 6, andcan be either manually controlled or can be controlled by the controlunit 34. Control unit 34 controls the steering section 36 in a similarmanner as it controls the propulsion section 22.

[0062] When push-pull wires 38 are moved together, the length of thesteering section 36 changes, and the tip 40 on distal end 4 of catheter2 is pushed further in the body cavity, or is withdrawn partially fromthe body cavity. If push-pull wires 38 are acted on differentially,steering section 36 can be turned in any direction relative to thelength of the catheter 2. Sutures 42 can be used to attach push-pullwires 38 at discrete locations on the flexible mesh 37, to control theirpositioning and to support them, so they can transmit compression forceswithout buckling.

[0063] Devices other than sutures 42 can be used to hold push-pull wires38 in position around steering section 36. For example, rigid rings canbe fixed at axial locations along the steering section 36, and thepush-pull wires 38 can be attached to the rings, or may be threadedthrough holes formed in the ring's outer portion. Alternatively, simpleclips or loops can be used to tie push-pull wires 38 to specific pointsof mesh 37, so the wires can move only in the axial direction. Heatshrink, polyurethane, or other type of low friction flexible claddingcan be applied on top of flexible mesh 37 and wires 38 to facilitateinsertion and travel of the device within the body cavity. The use of aslippery coating for the catheter makes it easier for the propulsionsection 22 to pull the catheter along the body cavity, and also reducediscomfort to the patient. The low friction coating can also be used onthe inside of the cladding, to reduce friction with push-pull wires 38.

[0064] In a further embodiment according to the invention, the steeringsection 36 can have an outer surface formed by bellows instead of theflexible mesh 37. The bellows can be inflated or deflated to extend orcontract, in a direction along the length of the catheter 2. Bellows canbe also extended and contracted by operation of push-pull wires 38,connected to tip 40. In this case, the bellows are used simply as anouter cover for the mechanism of the steering section 36, similarly tomesh 37. Holes can be formed at the crests of the bellows ridges, toguide and keep in place the push-pull wires 38. The inflatable bellowsactuators are further described in U.S. Pat. Nos. 5,181,452 and5,317,952 which are hereby incorporated by reference.

[0065] The inflation and deflation, or the extension of various bellowssections can be controlled either by hand or by a control unit 34. Useof the bellows allows steering section 36 to either change its length,or to change the direction where distal end 4 points, in a manneranalogous to that described above.

[0066] As a further alternative to a mesh or bellows, a coil structurecan be used to maintain the push-pull wires 38 in place, and to givesome structural rigidity to the steering section 36. One or more coilscan extend from tip 40 along the length of steering section 36, and canbe connected to wires 38 with any of the methods described above.

[0067] Sheath 11 defining working channel 10 preferably can be attachedto tip 40 but not to mesh 37. In this manner, mesh 37 can change lengthwithout affecting the shape of the working channel 10.

[0068]FIG. 3 shows a second embodiment of the catheter introducer systemfor endoscopy according to the present invention. As shown in FIG. 3, atube-like catheter 2 defines a working channel 10 and has a distal end 4designed for introduction in the body cavity. As described above, aresilient sheath 11 can be used to define the working channel 10. Nearthe distal end 4 of the catheter 2, there is a steering/propulsionsection 50 that is used both to pull the rest of the catheter along inthe body cavity that is being explored, and also to direct the distalend 4 of the catheter 2 in the desired direction.

[0069] Steering/propulsion section 50 comprises a steering/elongationportion 52 that provides elongation as well as steering functions forthe catheter introducer system 1′. For example, steering/elongationportion 52 can be formed by a mesh with push-pull wires similar to theone described in FIG. 2. If the push-pull wires are extended orwithdrawn at the same time, steering/elongation portion 52 elongates anddistal end 4 of the catheter 2 is extended further or is withdrawn fromthe body cavity. If the push-pull wires on one side ofsteering/elongation portion 52 are extended, while those generally onthe opposite side of the steering/elongation portion 52 are withdrawn,the steering/elongation portion 52 will turn towards the withdrawingwires, thus changing the direction in which distal end 4 is pointed. Acombination of elongation and turning commands can also be givensimultaneously to the steering/elongation portion 52. In a preferredembodiment, three wires 38 are equally spaced at 120° intervals aroundthe circumference of the steering/elongation portion 52, and can provideelongation and steering as described above.

[0070] Preferably, steering/elongation portion 52 is formed of aflexible mesh tube to which are attached push-pull wires 38. Thisconfiguration retains a large hollow working channel 10 inside thedevice because the integrated steering and propulsion mechanism takes uplittle wall thickness. Steering/propulsion section 50 also includes aproximal gripper portion 54 and a distal gripper portion 56 that arerespectively positioned at the proximal and distal ends ofsteering/elongation portion 52. Both the proximal and distal gripperportions 54 and 56 preferably include gripping pads 58 that havesuctions ports 59 that can selectively apply suction to the surroundinginner surfaces of the body cavity.

[0071] In the preferred embodiment, suction ports 59 are connected to avacuum system with a source 31 and ducts 33, so that when the vacuum isturned on the suction port 59 will attach to the tissue of thesurrounding body cavity. When the vacuum is turned off, suction port 59releases its grip on the inner surface of the body cavity. In adifferent embodiment of the invention, one or both of the proximal anddistal gripper portions can include other means of attaching themselvesto the inner surface of the body cavity, such as inflatable balloons,suction arms, or other known devices.

[0072] In a different embodiment, proximal and distal gripper portions54, 56 can include a perforated suction ring to apply vacuum to thesurrounding body cavity tissue, instead of discrete gripping pads 58with suction ports 59. Several configurations of perforated suctionrings will be described below.

[0073] In another embodiment according to the invention,steering/elongation portion 52 can include, for example, inflatablebellows as described above with reference to the steering section 36,instead of push-pull wires and flexible mesh. In yet another embodimentaccording to the invention, the push-pull wires can be replaced bylinear actuators 70 embedded within the flexible structure of catheter2, as shown in FIG. 4 and as earlier described.

[0074] Gripper portions 54, 56 move alternatively closer and fartherapart during the progression of catheter 2. The structures withinsteering/elongation portion 52 must therefore allow this movement. Forexample, as shown in FIG. 19, sheath 11 defining working channel 10 canbe formed by a flexible membrane 150 surrounded by coils 152. Thisconstruction results in a sheath 11 that can extend and contract axiallywhile retaining a constant cross section, and provides a smooth innersurface to the working channel 10. The tubes that provide suction todistal gripper portion 56 also have to extend and contract axially. Thiscan be achieved, for example, using bellows shaped tubes 154, or usingtelescoping flexible tubes 156, with seals 158 placed between thetelescoping sections.

[0075] The catheter introducer system 1′ shown in FIG. 3 includes anextremely flexible catheter 2 and is designed to pull itself along thebody cavity where it is introduced, rather than being pushed as is donewith traditional endoscopes. The catheter moves in an inchworm fashionby coordinated motion and control of the gripper portions and of thesteering/elongation portion.

[0076] For example, to move forward, the proximal gripper portion 54attaches to the tissue of the body cavity by applying a vacuum tosuction ports 59 of the proximal gripper portion 54. Thesteering/elongation portion 52 is then extended, so that the distalgripper portion 56 is pushed further inside the body cavity. Suctionports 59 of distal gripper portion 56 then apply a vacuum to thesurrounding tissue so as to attach to the tissue, and the suction ports59 of the proximal gripper portion 54 stop applying a vacuum. In apreferred embodiment, suction ports 59 can also eject pressurized air tocompletely release the surrounding tissue. At that pointsteering/elongation portion 52 is contracted while the distal gripperportion 56 continues to attach to the surrounding tissue, so that theportion of the catheter behind distal gripper portion 56 is pulled alonginside the body cavity by a distance substantially equal to thecontraction distance of steering/elongation portion 52. The process isthen repeated until the distal end 4 of the catheter 2 reaches thedesired position inside of the body cavity.

[0077] To move backward, the above process is reversed. For example, theproximal suction gripper 54 attaches to the tissue, while the distalgripper portion 56 releases the surrounding tissue. Steering/elongationportion 52 is contracted, so that the distal end 4 of the catheter 2 iswithdrawn from the body cavity. Proximal gripper portion 54 thenreleases the tissue, distal gripper portion 56 attaches to the tissueand the steering/elongation portion 52 is extended, so that the portionof the catheter 2 behind distal gripper portion 56 is withdrawn from thebody cavity. The order of attachment and release of grippers 54 and 56can also be reversed, as long as the contractions and extensions ofsteering/elongation portion 52 cause the catheter to be respectivelypulled towards or pushed away from a gripper portion 54, 56 that isattached to the tissue of the body cavity.

[0078] The catheter 2 can also simply be pulled out of the body cavityby the operator. These steps are repeated until the entirety of catheter2 is extracted from the body cavity. Throughout the operation, steeringis achieved by bending the steering/elongating portion 52 either whilethe insertion or extraction movement is carried out, or separately whilethe catheter 2 remains in position. As shown in FIG. 1, a control unit34 can be used to coordinate the operation of steering/propulsionsection 50, such as bending and elongation of steering/elongationportion 52, and application of suction.

[0079] The second embodiment according to the invention shown in FIG. 3also provides a large working channel 10 through which various endoscopytools can be inserted and positioned easily in the desired portion ofthe body cavity. A tool ideally suited for this device is a suctionpolypectomy device to remove polyps from the intestine. Theeffectiveness of such device is currently limited by the small workingchannel of existing endoscopes, but this drawback is resolved by usingthe catheter introducer system according to the invention.

[0080] Several variations can be made to the design of the gripping pads58 and 24 described above in conjunction to the embodiments of theinvention shown in FIGS. 1 and 3. These variations are designed tomaximize the traction or gripping force exerted by the gripping pads onthe surrounding tissue of the body cavity.

[0081] In one embodiment shown in FIG. 5, the gripping pads 58 can bereplaced by a perforated suction ring 100, having an outer surface 104with a plurality of holes 102. Independently controllable sources ofsuction and compressed air are provided to gripper portions 54′, 56′,which can be moved close together or apart along the steering/elongationportion 52, as described above with reference to FIG. 3. In thisexample, suction is applied to the surrounding tissue through holes 102.Holes 102 are designed to distribute the suction over a large area oftissue, so that the traction force generated is increased. A suctionring 100 with multiple holes 102 also reduces the chances that holes 102will be clogged by the tissue, or other debris or contaminants. Tofurther prevent clogging, provisions can be made to eject pressurizedair or a liquid from holes 102, to force any contaminants out of holes102.

[0082] Suction ring 100 also defines a buffer area, or plenum 101disposed between the perforated outer surface 104 and the suctionconnection duct 33, as shown in FIG. 6. Plenum 101 is used to separatethe suction duct 33 from the holes 102 on suction ring 100, so thatsuction is distributed to a larger area of tissue, and clogging of thevacuum supply is prevented. Plenum 101 can be, for example, an enclosedtoroidal volume between surface 104 and the center of suction ring 100.Plenum 101 may also be divided in non-communicating portions, eachconnected to a different section of suction ring 100.

[0083] An additional perforated screen can be placed under the surfaceof suction ring 100. This additional screen has holes smaller than holes102, and acts as a filter to further prevent clogging of duct 33. Holes102 can have a size optimized to maximize suction, while the holes ofthe additional screen are optimized to stop contaminants.

[0084] The push-pull wires used to control turning and elongation of thecatheter travel across at least one of the suction rings 100 beforereaching the distal portion 4 of catheter 2. Thus the wires must beinsulated from the suction source, to prevent vacuum leaks. For example,as shown in FIG. 5, the wires 38 could pass through a passage 120drilled through suction ring 100, sealed from the portions connected tothe suction. Alternatively, wires 38 could pass through a sealed tubecrossing plenum 101.

[0085] In different embodiments, holes 102 do not have to be uniformlydistributed around the outer surface 104 of perforated suction ring 100.For example, as illustrated in FIG. 7, the holes can be grouped inperforated sectors 106 separated by sectors 108 that are not perforated.Sectors 106 may be connected to separate sources of suction, so that ifone of the sectors becomes detached from the tissue, the remainingsectors will not be adversely affected, and will continue to apply fullsuction to the portions of tissue to which they are attached. In oneexample, holes 102 can have a diameter of approximately 0.04 in., andsectors 106 can extend for approximately 85 degrees of arc, and can beequally spaced around the circumference of suction ring 100.

[0086] As shown in FIG. 8, holes 102′ having a different size can beutilized on suction ring 100. For example, holes of a diameter of about0.02 in. can be formed. The size of the holes is optimized to obtain thebest suction without excessive clogging. Smaller and more numerous holestend to grip better the tissue, but clog more easily. Fewer larger holesclog less, but also tend to provide less traction on the tissue.Different sizes of holes can be used in all the configurations ofsuction ring 100 described here.

[0087] In a different embodiment, portions of suction ring 100 havingholes 102 can be recessed with respect to the rest of the outer surface104 of suction ring 100. For example, as shown in FIG. 9, recessedportions 121 have a plurality of holes 102 to apply suction to thesurrounding tissue. The remaining sectors 108 are not perforated. Thepurpose of this design is to obtain a configuration of the suction holes102 that increases traction by drawing portions of the body tissue inrecessed portions 121. As the previous configurations, the recessedpattern of FIG. 9 could be made with different size holes, and couldencompass different portions of suction ring 100.

[0088]FIG. 10 shows a configuration of suction ring 100 that isespecially advantageous when the body cavity is inflated with a gas, tofacilitate visual inspection and passage of medical instruments. When agas is forced in the cavity, such as the colon, it passes around thecatheter, and tends to detach portions of the outer surface of suctionring 100 from the surrounding tissue. If a portion of perforated suctionring 100 is detached, the rest of suction ring 100 also is likely tobecome detached from the tissue, especially if outer surface 104 isuniformly perforated. Axial ridges 122 assist in the formation of foldsin the tissue surrounding the suction ring 100. The gas forced pastsuction ring 100 can thus flow in a passage formed by the tissue folds,so that sectors 106 remain attached and keep the suction ring 100 inplace.

[0089]FIG. 20 shows another design that allows passage of gases forcedthrough the cavity. Suction ring 100 includes perforated sectors 106separated by grooves 160. Grooves 160 provide a channel for flowinggases, while perforated sectors 106 remain attached to the surroundingtissue.

[0090] In certain applications, it may be desirable to apply suction toonly a portion of the circumference of suction ring 100. FIG. 11 showsone example of such application, where a perforated sector 106 extendsover an arc of approximately 85 deg., and the rest of suction ring 100is not perforated. As described above, the pattern and size of holes 102can be optimized as desired. In addition, various features alsodescribed above can be included in this design, such as axial ridges 122shown in FIG. 12, and a recessed construction of perforated sector 106,shown in FIG. 13. As before, the purpose of these features is tomaximize traction and prevent separation of the entire suction ring 100from the body cavity tissue.

[0091]FIG. 14 shows a further embodiment of the suction ring 100, wherethe perforated sector 106 is recessed, and is further surrounded byperipheral ridges 126. Peripheral ridges 126 are disposed around therecess 124, and protrude above the outer surface 104 of suction ring100. Peripheral ridges 126 act as a seal that separates the portion ofcavity tissue on which perforated sector 106 applies a suction, and therest of the cavity tissue. In this manner, fluids can flow through thebody cavity while the catheter 2 is inserted in the body cavity. Theflow can pass between the non perforated sectors 108 of suction ring 100and the body tissue, while perforated sector 106 together withperipheral ridges 126 maintains a suction against the tissue, and isthus anchored in place.

[0092] As shown in FIG. 15, suction can be applied to the tissue byslots 132, rather than by round holes 102 described above. Slots 132 canbe used with any of the configurations described, and can be disposedperpendicular to the relative motion of catheter 2, as shown in FIG.15b.

[0093] The several configurations of suction ring 100 are especiallywell suited for use in conjunction with the proximal and distal gripperportions 54,56 shown in FIG. 3. However, the same configurations canalso be successfully utilized to maximize the traction generated bygripping pads 24 shown in FIG. 1.

[0094] The traction force that can be generated by the propulsionsections of catheter 2 can be increased by increasing the folds andundulations of the cavity tissue in contact with the suction ring 100,thus generating an interference between the tissue of the inner surfaceof the body cavity and fixed protrusions of the gripping pads 24, 58.For example, suction can be used to draw some tissue in holes, slots orbetween protrusions formed on suction ring 100. Folds in the tissue theninteract with the edges of these structures to generate a force opposingthe relative motion between the tissue and suction ring 100 greater thanwould be possible if the two were simply sliding past each other.

[0095]FIG. 16 shows one possible exemplary embodiment utilizing thisprinciple. Tissue 200 of the inner surface of a body cavity is partiallydrawn inside hole 102 formed in perforated sector 106 of suction ring100. As suction ring 100 mounted on catheter 2 is moved in a relativedirection A, a force F_(A) resisting the relative motion is applied bythe portion of tissue 200 that is drawn by suction inside hole 102. Tofurther increase this traction force, means can be employed to urge theportion of tissue 200 drawn within hole 102 against the perimeter ofhole 102. For example, inflatable parts 150 could be inflated, as shownby dashed line 152, to hold tissue 200.

[0096] In a different embodiment shown in FIG. 16b, after being drawninside hole 102, tissue 200 can be trapped between a sleeve 153 and theperimeter of hole 102. For example, sleeve 153 can be concentric withthe suction ring 100, and be rotatable or translatable just inside ofouter surface 104.

[0097] A different exemplary embodiment of a design to increase tractionforces is shown in FIGS. 17 and 18. In this case, protrusions extendfrom the surface of suction ring 100 to interact with the tissue that isdrawn between the protrusions by suction. As shown in FIG. 17, theprotrusions can be, for example, ridges 136 disposed in a substantiallycircumferential direction around suction ring 100. Suction holes 102 canbe disposed between the ridges 136, or even on the raised sides of theridges 136. Instead of ridges, suction ring 100 can have a “soap dish”surface construction, where a plurality of studs 138 extend from theouter surface, and are interspersed with suction holes 102. Thisembodiment is shown in FIG. 18. To maximize the resistance to relativemovement between the catheter and the tissue, the studs can be staggeredin the direction of relative movement. The designs shown in FIGS. 17 and18 take advantage of the same mechanism described with reference to FIG.16.

[0098] The force exerted by gripper portions 54, 56 can also be variedby changing the axial length of suction ring 100, and the number of rowsof holes 102. For example, FIG. 21a shows a suction ring 100′ having twoadditional rows of holes 102, in the axial direction of the catheter.FIG. 21b shows the same suction ring 100′ used in a gripper portion 54,56, to generate a greater force.

[0099] An example of how the catheter introducer system according to theinvention can be used will now be described with reference to FIGS. 1through 3. A common procedure in endoscopy is the examination of thecolon and removal of polyps present in the colon. A vision light tool(VLT) is inserted into the steering catheter 2 and is secured to the endof the catheter 2. Catheter 2 is then inserted into the rectum using arigid sheath 20. The catheter 2 is then driven through the intestinetowards the cecum while being guided and controlled by a control unit34. In one embodiment according to the invention, control unit 34includes a monitor through which the operator can view what is beingtransmitted by the VLT, so that he can drive the catheter forward orbackwards while simultaneously steering it. During tests, the propulsionsection was able to resist a pulling force of approximately 2.5 lbs.while remaining attached in position in a colon by suction.

[0100] After reaching the cecum, the device is then slowly pulled backfrom the cecum to the rectum, as the interior of the intestine isinspected. When a polyp is sighted, a suction polypectomy device isinserted into the catheter until it protrudes from the distal end 4 ofcatheter 2, and is seen on the monitor by the operator. The suctionpolypectomy tool is steered to the polyp, and the polyp is excised andwithdrawn by vacuum through the suction channel of the polypectomy tool.Additional tools can be introduced and brought into position at the siteof interest rapidly and easily through working channel 10, becausecatheter 2 maintains access to the operation site while various toolsare withdrawn and inserted back into the catheter.

[0101] In a preferred embodiment according to the invention, the variousdiagnostic and therapeutic tools used in endoscopy are positionedaccurately with respect to the body cavity by moving the distal end 4 ofthe catheter 2 with the steering section 36, or with thesteering/propulsion section 50. In a different embodiment, still withinthe scope of the invention, the endoscopic tools can be positionedaccurately by using a separate positioning system, which could includepush-pull wires 72 similar to those shown in FIG. 2, or a systemincluding inflatable bellows, linear actuators, or a combination ofthese devices. Also in a preferred embodiment according to theinvention, many components of the catheter introducer system aredisposable, thus assuring a high degree of sterility to the device. Forexample, the flexible tube of catheter 2 can be disposable, as well asvarious portions of the endoscope tools 8 used within working channel10.

[0102] In a different embodiment of the catheter introducer systemaccording to the invention, the steering section may be separate fromthe propulsion section, and the propulsion section includes an evertingtube that provides the force to push the catheter further in the bodycavity. As shown in FIG. 22, catheter 2 has a distal end 4 that isintroduced in the body cavity, and a steering section 36 analogous tothe steering section described with reference to FIG. 1. Propulsionsection 300 includes an everting tube mechanism that pushes from insidethe body catheter 2 along the body cavity.

[0103] Everting tube mechanism 302 includes a flexible everting tube 304that has an external surface 306 divided into an outer portion 309 andan inner portion 308, separated by a fold 310. An anchor 312 may bemounted around the catheter 2 and everting tube 302, and may be securedso that it does not move relative to the body cavity. For example,anchor 312 can be secured to the opening of the body cavity. The outerportion 309 of the everting tube 302 may be securely attached to anchor312, while the inner portion 308, together with catheter 2, is free toslidably translate relative to anchor 312. An analogous design which isnot shown can also be produced where the inner portion is attached to ananchor element, while the outer portion is free to translate with thecatheter, relative to the anchor element.

[0104] The lengths of inner and outer portions 308, 309 are notconstant. As will be described below, the fold 310 is forced to moveaway from anchor 312 to propel the catheter. As fold 310 moves away fromanchor 312, the length of flexible tube 304 between anchor 312 and fold310 increases. Because outer portion 309 is attached to anchor 312, theincreased length is provided by a section of inner portion 308 that isturned over at fold 310, and becomes part of outer portion 309. At thesame time, the portion of flexible tube 304 on the opposite side ofanchor 312 decreases in length as inner portion 308 translates pastanchor 312.

[0105] A drive system is used to cause the flexible tube 304 totranslate relative to the body cavity. In one embodiment, a fluid isprovided inside of flexible tube 304. The fluid is pressurized so thatflexible tube 304 is kept somewhat rigid, and to provide a force thatpushes fold 310 away from anchor 312. For example, a pressurizationsystem 314 can provide fluid pressurized by a pump that is conveyed toflexible tube 304 by fluid distribution lines 316. A control unit 320can be used, for example, to operate the pressurization system 314 viacontrol lines 322. In one exemplary embodiment, a greater fluid pressurecan be applied to the portion of the flexible tube 304 between anchor312 and fold 310, so that the pressure forces fold 310 to translate awayfrom anchor 312. One skilled in the art would appreciate that a seal(not shown) attached to the outer portion 309 and abutting the innerportion 308, such that inner portion 308 can slidably translate adjacentthe seal, would permit the pressure force to translate fold 310 awayfrom anchor 312.

[0106] A second pressurization system 332 can also be included topressurize lubricating fluid placed between the everting tube 304 andthe surface of the catheter 2. As shown in FIG. 23, a fluid pocket 330can be formed and filled with fluid to lubricate the relative movementof the everting tube 304 and the catheter 2. This second pressurizationsystem 332 reduces frictional forces caused by movement of the evertingtube 304 relative to the catheter 2. The second pressurization system332 can be used to pressurize the fluid in pocket 330, under the controlof a controller 334. Alternatively, control unit 320 and pressurizationsystem 314 can also be used to control the state of the fluid in pocket330.

[0107] In one exemplary embodiment shown in FIG. 22, a thrust collar 322is attached to catheter 2, and is shaped to receive the fold 310 offlexible tube 304. In this manner, as fold 310 is forced away fromanchor 312, a force is applied to thrust collar 322, and the entirecatheter 2 slidably translates in a direction away from anchor 312. Inone embodiment, the fluid that pressurizes flexible tube 304 is alubricant used to facilitate movement of the inner and outer portions308, 309 relative to each other, and relative to other components of theeverting tube.

[0108] In a different embodiment of the everting tube according to theinvention, the drive system includes a mechanical drive used totranslate the inner portion 308 of flexible tube 304 away from ortowards anchor 312. This motion, in turn, causes catheter 2 to move inthe same direction. In one exemplary embodiment, the mechanical driveincludes wheels 324 that rotate to impart a translational movement toinner portion 308. Wheels 324 can be, for example, gears or frictionwheels that engage the flexible tube. Propulsion for the wheels 324 canbe provided by a transmission mechanism or a gear drive extending alongcatheter 2, or by a remote system actuating the wheels by magnetism orother interaction.

[0109] Control unit 320, or a separate control unit, can be used toactuate wheels 324 of the drive mechanism. As indicated in FIG. 22,wheels 324 can rotate in either direction, to further insert or toretract catheter 2 from the body cavity. A combination of a mechanicaldrive and of pressurized fluid, as described above, can also be used topositively control the movement of catheter 2. Retraction may beaccomplished by attaching another thrust collar (not shown) adjacent theproximal end 6 of catheter 2 that is shaped to receive another foldlocated at the proximal end of the flexible tube 304. In this manner, asthe proximal thrust collar is forced away from anchor 312, a force isapplied to the proximal thrust collar, and catheter 2 slidabletranslates in a direction away from anchor 312 and out of the patient'sbody. Catheter 2 may also be retracted by exerting a pulling force oncatheter 2 separately or in conjunction with the drive units discussedabove.

[0110] In one embodiment, the everting tube can be manufactured from amaterial having azotropic properties, so that it will stretch in onedirection, but resist stretching in the perpendicular direction. Forexample, the everting tube can be made of Silicone, PTFE or PE. Theeverting tube can be made with or without reinforcing material such as abraid.

[0111] As indicated, the catheter introducer system of the presentinvention could be used to navigate within body cavities other than theGI tract. For example, air passages or blood vessels could be exploredusing this system. For blood vessels, it would be necessary to reducethe size of the apparatus, and preferably to only use the steeringsection, to avoid interference with blood flow through the vessel. Forexample, an outer diameter of the device would have to be less thanabout 2 mm.

[0112] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the structure and themethodology of the present invention, without departing from the spiritor scope of the invention. Thus, it is intended that the presentinvention cover the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. A self propelling catheter introducer system forexploring a body cavity, comprising: a flexible tubular catheter havinga length extending from a distal end for introduction in the cavity to aproximal end opposite the distal end; a tubular working channel formedwithin the catheter, adapted for guiding medical tools along the lengthof the catheter; a steering section of the catheter disposed adjacentthe distal end, adapted for pointing the distal end in a desireddirection; and an everting tube applying a propulsive force to thetubular catheter.
 2. The system according to claim 1, further comprisinga control unit for controlling operation of at least one of the evertingtube and steering section.
 3. The system according to claim 1, furthercomprising a light vision tool detachably connected to the distal end ofthe catheter.
 4. The system according to claim 1, wherein the evertingtube comprises: a flexible tube having an external surface folded onitself, the external surface defining an outer portion substantiallynon-moving relative to the body cavity, and an inner portion adjacentthe tubular catheter; at least one thrust collar secured to the tubularcatheter, adapted to transmit a force from the flexible tube to thetubular catheter; and a drive unit adapted to selectively translate theinner portion relative to the outer portion of the external surface. 5.The system according to claim 4, further comprising an anchor disposedaround the tubular catheter at a point of entry of the body cavity, theanchor being substantially stationary relative to the body cavity. 6.The system according to claim 5, wherein the outer portion is attachedto the anchor.
 7. The system according to claim 5, wherein the innerportion is attached to the anchor.
 8. The system according to claim 4,wherein the drive unit is a gear drive to translate longitudinally theinner portion.
 9. The system according to claim 4, wherein the driveunit is powered from outside the body cavity.
 10. The system accordingto claim 8, wherein the gear drive applies a force to a surface of theflexible tube.
 11. The system according to claim 4, wherein the flexibletube material has azotropic properties.
 12. The system according toclaim 4, wherein the flexible tube is made of one of silicone, PTFE, andPE.
 13. The system according to claim 4, wherein the flexible tube ismade with a reinforcing material.
 14. The system according to claim 13,wherein the reinforcing material is a braid.
 15. The system according toclaim 4, wherein the flexible tube contains a fluid.
 16. The systemaccording to claim 15, wherein the fluid is a lubricant.
 17. The systemaccording to claim 4, wherein the drive unit comprises a pressurizedfluid selectively applying a pressure force to an internal surface ofthe flexible tube.
 18. The system according to claim 17, furthercomprising a pump for pressurizing the pressurized fluid and a line fordistributing the pressurized fluid.
 19. The system according to claim17, further comprising a control unit for controlling pressurization ofthe fluid contained in the everting tube.
 20. The system according toclaim 8, further comprising a control unit for controlling movement ofthe gear drive.
 21. The system according to claim 4, further comprisinga control unit for controlling operation of the drive unit.
 22. Thesystem according to claim 1, wherein the steering section comprises aplurality of push-pull wires secured to the distal end of the catheter,circumferentially disposed along the length of the catheter, adapted tobe individually extended and retracted to point the distal end in thedesired direction.
 23. The system according to claim 22, wherein thesteering section further comprises a flexible tube-like structure toguide movement of the plurality of push-pull wires.
 24. The systemaccording to claim 1, wherein the steering section comprises bellowsthat can be extended and contracted in a direction along the length ofthe catheter, and control wires disposed circumferentially around thecatheter to control extension of the bellows, thus pointing the distalend in the desired direction.
 25. A method of propelling a catheter forexploring a body cavity, the catheter having an outer surface includingan everting tube, comprising: inserting a distal end of the catheterthrough an opening of the body cavity; securing an anchor portion of thecatheter to the opening, the catheter being slidable in the anchorportion, a surface of the everting tube being secured to the anchorportion; and translating the everting tube relative to the anchorportion, thus inserting into or withdrawing the catheter from the bodycavity.
 26. The method according to claim 25, further comprisingproviding a pressurized fluid in the everting tube, such that afolded-over end of the everting tube translates relative to the anchorportion, the folded-over end abutting a thrust collar secured to thecatheter to apply a propulsive force to the catheter.
 27. The methodaccording to claim 25, further comprising activating a drive mechanismto translate a portion of the everting tube in contact with the catheterrelative to the anchor portion.